BART police arrested a 15-year-old Hayward boy Tuesday night on suspicion of throwing the playground equipment onto the BART tracks in an effort to wreck a train.

Rodriguez said a similar incident occurred Saturday night when a 10-foot metal pole bearing a "No Parking" sign was thrown across the tracks in the same area.

Damage from the two incidents are estimated at a quarter-million dollars, Rodriguez said.

The teenager was booked into Alameda County juvenile hall on two felony counts of attempted train wrecking, he said, and is likely to be charged with both incidents.

Rodriguez said BART police went door to door in the neighborhood around the tracks after Tuesday's incident and found witnesses who pointed them to the youth.

"It was just nitty-gritty, back-to-basics police work," said Rodriguez. "They canvassed the neighborhood and talked to people, and we believe we've got the right guy."

The accident shut down BART traffic between Hayward and Fremont for almost three hours as firefighters and BART crews helped passengers to safety and then cleared away the crippled train.

Fifty passengers were evacuated from the train that hit the teeter-totter and another 47 from a Daly City-bound train behind it that was stranded when the system's electric power shut off automatically, a built-in safety feature.

Rodriguez said a rescue train was sent southbound to the stalled northbound trains and passengers crossed onto the rescue train on planks thrown between the cars.

Full service was restored on both tracks about 3:30 p.m. Tuesday.

The collision Saturday evening with the sign pole caused a similar mess, said Rodriguez, putting the train out of service and shutting down the line.

All 95-miles of BART track around the Bay Area are fenced off from public access, so getting a teeter-totter onto the tracks is not easy. The metal equipment was hurled over a fence or dropped from a nearby overpass, said Rodriguez.&lt;